That's because the Black Panthers never actually left.
On the 50th anniversary of the founding of the Black Panther Party, people are taking a second look at the group. A mesmerizing new film, "Black Panthers: Vanguard of the Revolution," airs on PBS throughout this month and appears online. And Beyonce's tribute caused people to post vintage photos of the Panthers on social media sites and debate the group's purpose.
"They're always going to be a potent symbol because we live in a visual age," says Komozi Woodard, a history and Africana studies professor at Sarah Lawrence College in New York.
"The way they dressed, the way they walked, the visual body of their work and their rhetoric" -- it all "captured peoples' imagination."
It still does. Here are three reasons why.
No. 1: Using words as weapons
People focused on the guns they carried, but the Panthers did a lot of damage with their words. They transformed political discourse into a form of verbal combat.
"Using words as a weapon was born with the Panthers," Woodard says.
The PBS documentary shows how. Directed by Stanley Nelson, recipient of a MacArthur "Genius" grant, the film is filled with electrifying moments: armed Panthers squaring off against grim police officers; jaw-dropping revelations about the FBI's successful campaign to infiltrate the Panthers; aging Panthers recounting the battles they fought and friends they lost.
Yet the way the Panthers spoke is as memorable as how they looked, the film reveals. They weaponized words. Consider how a smirking Eldridge Cleaver, a Panther leader, responded to Ronald Reagan when the then-governor of California criticized the group for carrying guns in public.
"I challenge Ronald Reagan to a duel to the death because Reagan is a punk, a sissy and a coward," Cleaver said during a Stanford University speech in a clip from the film. "He can fight me with a gun, a knife or a baseball bat. I'll beat him to death with a marshmallow."
Or consider the origin of the Panthers' word for the police: "pigs." It seemed like a juvenile and cruel insult, but there was a purpose behind it, explains Huey Newton, co-founder of the Panthers, in "Voices of Freedom," an oral history of the civil rights movement.
"Most of my young life I was a student. And I know sociologically that words stigmatize people," Newton said. "We felt that the police needed a label, a label other than that fear image that they carried in the community. So we used the pig as the rather low-life animal in order to identify the police. And it worked."
The Black Panther Party was formed for the same reasons that galvanized the Black Lives Matter movement -- police brutality in the black community. Newton and others started the group in 1966 at a time when urban riots were spreading across America. Many of the riots were sparked by the beating or killing of blacks by police under suspicious circumstances.
Newton found a loophole in California law that allowed the Panthers to police the police. It allowed the open carry of loaded weapons. The Panthers used that loophole to monitor police patrols in black neighborhoods to ensure no black person was mistreated.
The Panthers, not the NRA, were the first American political group to fiercely defend the Second Amendment right to bear arms and were originators of the open-carry movement.
The Panthers' ambition, though, was bigger than guns. Many were Marxists who talked openly about political revolution and wealth redistribution in their mission statement, the Ten-Point Program. The group also provided free clinics and held very successful breakfast programs for poor black kids and gave women prominent roles in the movement.
The Panthers were so good at using words as weapons because they knew the transformative power of the written word. Many were voracious readers who reinvented themselves through books, often while in prison. Cleaver became a literary superstar when he wrote a best-selling memoir, "Soul on Ice." Newton transformed himself from an illiterate to a college law student who eventually earned a doctorate. Bobby Seale, a Panther co-founder, once subscribed to 22 political magazines and devoured books like "Before the Mayflower," a history of black America.
Kathleen Cleaver, a former Panther leader, says people focused on the Panthers' brawn, not their brains. She tells a story about a young man who joined the Panthers and asked a leader about getting a gun. The Panther gave him a stack of books instead.
"I thought you were going to arm me?"
"You are armed now."
The Rev. Martin Luther King Jr., according to singer Harry Belafonte, loved listening to the way the Panther leaders spoke. King once said of them:
"Were I able to co-opt those minds into my cause, there is no question that victory would be swift and eternal."
The Panthers' rhetoric did eventually lead to a revolution -- in music and politics, some say.
There would be no hip-hop music without the Panthers, some claim. The Panthers' refusal to turn the other cheek, their in-your-face speeches, their urban roots and Pan-African worldview -- all shaped the sensibility of hip-hop music.
It's no coincidence that a Panther, Afeni Shakur, gave birth to a son who would become a hip-hop legend -- Tupac Amaru Shakur -- says Caril Phang, author of "Birth of a Beat: How Kana:ta' Creates World Music," a book that examines how marginalized people use music to combat oppression.
Tupac Shakur was named after an Inca Indian chief who was put to death after leading a rebellion against Spanish colonial rule, she says.
"This child would grow up to be the greatest rap artist of all time," Phang says. "The fact that she named her son Tupac Amaru says a lot about the vision of the world that she wanted for her child. Those were the kind of ideas that built up the Panthers."
Phang sees the Panthers' influence in another modern politician who has weaponized words: Republican presidential candidate Donald Trump. Trump has insulted Mexicans, women and the disabled. He's said Hillary Clinton got "schlonged" and indirectly referred to another rival as a "pussy."
Trump is relying on a rhetorical strategy that Panther leaders used years ago, she says.
"Trump is playing to many of the elements that the Panthers employed in their strategies -- the more brash you are, the more attention you get."
No. 2: The audacity of swagger
The Panthers didn't just introduce a new look to pop culture with their leather jackets and berets. They brought a new attitude.
Call it the audacity of swagger.
Swagger -- a cocky, strutting, chest-thumping confidence -- pervades American culture today. An NBA player talks trash after dunking. Rapper Kanye West writes a song that declares, without irony, "I am a God." Even President Obama showed a little swagger when -- mimicking a Jay Z lyric -- he brushed the imaginary dirt off his shoulder while talking about critics.
The Panthers were the pioneers of this kind of performance art, some say. They injected swagger into the American mainstream at a time when civil rights groups were singing "We Shall Overcome" and demonstrators still dressed in their Sunday best.
The Panthers burst onto the American scene with an ultimate act of swagger. They strutted onto the floor of the California Assembly during a 1967 session carrying loaded guns to protest a proposed bill which targeted the Black Panthers' armed patrols and banned the open carrying of weapons in the state. News accounts of their dramatic entrance put them on the map.
"The days of polite protest were swept away by the Panthers," says Phang, the author.
The Panthers' swagger was built in part on their ability to craft memorable images. Before anyone ever talked about "branding," the Panthers were doing it.
"They had photographers follow them around," Woodard says. "Some of the other [black militant] groups didn't even want photographers around."
Prior to the rise of social media, the Panthers learned how to create a viral image before the term even existed. One of their iconic images is a poster of Newton, arrayed in a beret and black leather jacket, seated in a wicker fan-back chair with a rifle and an African spear. The image says everything; it doesn't need a caption. The poster spread like a hit song through the nation's black community.
"Nobody knew who Huey Newton was in the beginning -- they just knew that picture," says Woodard, the Sarah Lawrence college professor.
The group even produced one of the most influential visual artists of the '60s, a man once dubbed the "Norman Rockwell of the ghetto." His name is Emory Douglas. His graphic cartoons, often depicting cops as pigs and poor people as noble and resolute in the face of oppression, ran in the Panther newspaper. His art is now on display in Latin America, Australia and Europe.
The Panthers, however, didn't create black militancy. They were part of a general rise in black militant groups that began with Malcolm X. Black militants such as H. Rap Brown and Stokely Carmichael also talked about a "black revolution." But none of those groups or leaders knew how to use television to get their message across like the Panthers, says Woodard.
"The Panthers stole all of the oxygen in the room," Woodard says.
The Panthers' swagger, though, sometimes led to misconceptions about the group. Their defiant public image convinced many that they hated white people. That fear resurfaced in 2008 when Fox News reported that two members of the "New Black Panther Party," one carrying a nightstick, stationed themselves outside a Philadelphia polling station in an effort to intimidate white voters.
But "hating whitey" was not part of the Panthers agenda. The Panthers forged alliances with white, Asian and Latino political groups in America and abroad.
Bobby Seale, one of the Panthers' founders, declares in the film: "We don't hate nobody because of their color. We hate oppression."
No. 3: Unmasking the police
What would the Panthers have done with all of today's viral videos of people of color being mistreated by police officers?
It's an intriguing question because as long as 50 years ago, before complaints of a "New Jim Crow" or the mass incarceration of young black men, the Panthers were telling Americans that the criminal justice system was racially biased.
Their message was dismissed at the time, but resonates today because of protests over police brutality in cities like Ferguson and Baltimore, says Nelson, director of the PBS documentary.
"People look at the story completely different than they might have looked at the story two years ago," Nelson says of his film. "It's hard to say that these are just a group of militant radicals that hated the police. You see much more clearly that they had a point about police brutality. They were saying if nobody else will help the community, then we'll do it."
There's a cruel irony about the Panthers, though. They were created to expose police brutality, but it was their destruction that ultimately proved their point about law enforcement.
There's no doubt that part of their demise was self-inflicted. Some Panther leaders became power hungry, thuggish, and infatuated with violence. Some ambushed, wounded and killed police officers.
Even today there are those who say the Panthers demonized all police officers. Former New York City mayor Rudy Giuliani, for example, criticized Beyonce's Super Bowl homage to the Black Panthers saying that it amounted to an attack on police officers.
"What we should be doing in the African-American community, and all communities, is build up respect for police officers," Giuliani said, "and focus on the fact that when something does go wrong: OK, we'll work on that. But the vast majority of police officers risk their lives to keep us safe."
But it was former FBI Director J. Edgar Hoover who may have been most responsible for decimating the Panthers. He was obsessed with the group. In 1969, he said the Panthers were "the greatest threat to the internal security of our country." He created the COINTELPRO (counterintelligence program) to destroy them. COINTELPRO documents stated that the FBI wanted to prevent the rise of a "Black Messiah" political figure who would command a large following.
Depending on your point of view, COINTELPRO is either one of the most successful efforts to destroy a domestic terrorist group -- or a shameful chapter in U.S. history when the nation operated more like a police state than a democracy.
Through COINTELPRO, the FBI placed informants inside the Panthers, provoked violent internal feuds among Panther leaders through anonymous letters, and planted agent provocateurs in Panthers meetings to stir up talk about armed uprisings that would be used later to justify violent police raids.
In one infamous case, the FBI and Chicago police simply assassinated a "Black Messiah," one of the Panthers' most promising leaders, Nelson's film suggests and some historians claim.
That leader was Fred Hampton. He was the 21-year-old head of the Illinois branch of the NAACP. As one Panther said in Nelson's film, Hampton had that intangible "it" that drew people. He was a NAACP leader in high school, a charismatic speaker and a skillful organizer.
Hampton was expected to become a national leader. The Panthers were reeling from infighting and police raids by 1969, and some hoped that Hampton would give new life to the group.
"Fred Hampton was the best second chance for the Black Panther Party," Woodard says. "He was able to go into formerly racist white communities in Chicago and set up free clinics in their neighborhood and invite black people to come. That was a giant leap forward."
Acting on a tip from an FBI informant (a Hampton bodyguard who later killed himself), Chicago police burst into Hampton's apartment during an early morning raid on December 4, 1969, and shot him to death in his bed while his pregnant girlfriend watched.
Some officers were photographed grinning as they carried Hampton's corpse in a body bag outside his home. At least 76 shells from police guns were found in Hampton's apartment. One shell belonging to a Panther was recovered.
Hampton's death still divides people today. A grand jury indicted the police officers but none were convicted. The state of Illinois, the city of Chicago, and the federal government eventually paid a $1.85 million settlement to Hampton's family and survivors of the raid.
There were some Panthers, though, who refused to suffer Hampton's fate.
One of the most gripping moments in the PBS film comes when Nelson interviews members from one such group. Four days after Hampton's death, the newly formed Los Angeles Police Department's SWAT unit conducted another predawn raid on a Panthers office. With a "no-knock warrant," they burst through the front door with guns blazing. But these Panthers were ready.
They had fortified the office and drove SWAT officers back with a barrage of fire from Thompson submachine guns and shotguns. For five hours, a handful of them -- some just teenagers and others women -- held off a group of heavily armed police officers that would eventually swell to 300.
Surrounded and outgunned, the Panthers only surrendered after running out of bullets. No one on either side was killed, but several were wounded. The Panthers arrested in the shootout were later acquitted of the most serious charges in a lengthy trial.
One of them, Wayne Pharr, then only 19, was asked by a narrator in the PBS film how he felt when he was surrounded and death seemed imminent.
A jovial man with a scraggly silver beard, Pharr suddenly stopped smiling when he heard the question. He looked away and then he turned back to fix his interviewer with a look of unblinking intensity.
"I felt absolutely free. I was a free Negro, you understand?" he said. "I was making my own rules. I was the king of my domain. You couldn't get in. I couldn't get out. But in my space I was the king."
Pharr went on to become a real estate agent in Southern California and a community activist before dying of cancer in 2014.
Kathleen Cleaver, the Panther veteran who became one of their most charismatic leaders, says Panther members knew the risks.
"People have been murdered for less than what the Black Panthers did," she says. "So the question was for us: 'Do you want to live on your knees or die on your feet?' "
Cleaver doesn't question why groups like "Black Lives Matter" are still fighting some of the same battles that the Panthers fought 50 years ago.
"The use of extralegal brutal violence and terrorism against black people seems to be a key part of the American experience," she says. "It didn't end with the Civil War, World I, or Vietnam. I'm not surprised that it hasn't ended now."
Though they made a big splash, is it fair to say that the Panthers failed? The group all but disbanded in 1977. Newton was killed by a young gang member in 1989 during a dispute over drugs, not far from where the first Black Panther chapter was founded.
"The Panthers were torpedoed, arrested and they were murdered," says Cleaver, now a law professor at Emory University in Georgia. "We didn't have a chance to fail."
Yet somehow their example lives on. There are offshoots of the Panthers today in places like Israel, India and New Zealand, Woodard says.
"It's amazing that they went as far as they did."
And the Panthers can still claim at least one victory, suggests Nelson, director of the PBS film.
"The Panthers started off with nothing," Nelson says, "but are still being talked about 50 years later."
The revolution the Panthers fought for never came. But they changed America in ways that are still being felt. They made new rules in the world of politics and pop culture.
And in some ways, they are still the kings, and queens, of their domain.